HYDROLYSIS OF PHOSPHATOPENTAAMMINECOBALT(III) IN AQUEOUS SOLUTION

The kinetic parameters of the hydrolysis of phosphatopentaamminecobalt(III) in aqueous solution at unit ionic strength have been measured. The following hydrolysis constants were determined: for Co(NH3)6PO40, k(60°) = 2.0 × 10-6 sec-1, ΔH≠ = 39.6 ± 1.4, ΔS≠ = 33.7 ± 4.5; for Co(NH3)5HPO4+, k(60°) = 1.05 × 10-6 sec-1, ΔH≠ = 26.8 ± 0.5, ΔS≠ = -6.6 ± 1.5; for Co(NH3)5PO4H22+, k(60°) = 1.57 × 10-5 sec-1, ΔH≠ = 23.3 ± 0.3, ΔS≠ = -11.2 ± 1.0; for the base-catalyzed hydrolysis of Co(NH3)5PO40, k(60°) = 4.0 × 10-4 M-1 sec-1, ΔH≠ = 36.8 ± 0.7, ΔS≠ = 36.0 ± 2.0, where the units of ΔH≠ and ΔS≠ are kcal mol-1 and cal deg-1 mol-1, respectively. © 1969, American Chemical Society. All rights reserved.